Dual rotor, coreless, electromagnetic machine

ABSTRACT

A coreless electromagnetic machine includes a dual rotor and a stator. The dual rotor is adapted to rotate about an axis, and includes inner and outer rotor segments. The outer rotor segment is spaced radially outward from, and axially aligned to, the inner rotor segment. The inner and outer rotor segments radially define an annular chamber. The stator is disposed, at least in-part, in the annular chamber.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.62/616,496 filed Jan. 12, 2018, which is incorporated herein byreference in its entirety.

BACKGROUND

The present disclosure relates to electromagnetic machines, and moreparticularly to a dual rotor, coreless, electromagnetic machines.

Designing electromagnetic machines, such as electric motors, oftenrequires standardizing some dimensions while allowing the motor to varyin other respects to cover an entire range of operating requirements. Inone example and for a family of motors each providing differentoperating characteristics, an outer diameter of the motor may beconsistent, while the motor axial length (i.e., packaging length) ischanged to accommodate different windings. Improvements in motor designtechniques that may lead to improvements in motor efficiency, motorcooling, reduction in costs, and standardization of parts and packagingis desirable.

SUMMARY

A coreless electromagnetic machine according to one, non-limiting,embodiment of the present disclosure includes a dual rotor adapted torotate about an axis, the dual rotor including inner and outer rotorsegments, wherein the outer rotor segment is spaced radially outwardfrom and axially aligned to the inner rotor segment, and the inner andouter rotor segments radially define an annular chamber; and a statordisposed at least in-part in the annular chamber.

Additionally to the foregoing embodiment, the coreless electromagneticmachine is a coreless electric motor.

In the alternative or additionally thereto, in the foregoing embodiment,each one of the first and second rotor segments include a plurality ofpermanent magnets.

In the alternative or additionally thereto, in the foregoing embodiment,the plurality of permanent magnets are sintered magnets.

In the alternative or additionally thereto, in the foregoing embodiment,the plurality of permanent magnets are molded magnets.

In the alternative or additionally thereto, in the foregoing embodiment,the outer rotor segment and the stator radially define an annular outergap as part of the annular chamber, and the inner rotor segment and thestator radially define an annular inner gap as part of the annularchamber.

In the alternative or additionally thereto, in the foregoing embodiment,the stator includes a plurality of electric coils each including aninner winding layer wound about and spaced from a centerline thatgenerally intersects the axis, and the inner winding layer defining anopening for the flow of cooling air between the annular inner and outergaps.

In the alternative or additionally thereto, in the foregoing embodiment,each one of the plurality of electric coils include a plurality ofmid-winding layers disposed radially from the inner winding layer, andan outer winding layer disposed radially outward from the plurality ofmid-winding layers with respect to the centerline.

In the alternative or additionally thereto, in the foregoing embodiment,the stator includes a bonding material for securing the plurality ofelectric coils together.

In the alternative or additionally thereto, in the foregoing embodiment,the bonding material is molded to the plurality of electric coils.

In the alternative or additionally thereto, in the foregoing embodiment,the stator include a support structure, a plurality of bobbinsdetachably fitted to the support structure, and a plurality of electriccoils with each one wound about a respective bobbin of the plurality ofbobbins.

In the alternative or additionally thereto, in the foregoing embodiment,each bobbin of the plurality of bobbins define an opening for the flowof cooling air radially between the annular inner and outer gaps.

In the alternative or additionally thereto, in the foregoing embodiment,the cordless electromagnetic machine includes a motor drive disposed inan inner cavity axially aligned to and defined by the inner rotorsegment, wherein the inner rotor segment is radially disposed betweenthe inner cavity and the annular chamber.

In the alternative or additionally thereto, in the foregoing embodiment,the motor drive includes a circuit board electrically connected to eachone of the plurality of electric coils.

A coreless electric motor according to another, non-limiting, embodimentincludes a dual rotor adapted to rotate about an axis, the dual rotorincluding inner and outer rotor segments each including a plurality ofpermanent magnets, wherein the outer rotor segment is spaced radiallyoutward from and axially aligned to the inner rotor segment, and theinner and outer rotor segments radially define an annular chamber; astator disposed at least in-part in the annular chamber, and including aplurality of electric coils; and a motor drive electrically connected toeach one of the plurality of electric coils.

Additionally to the foregoing embodiment, the inner rotor segmentradially defines an inner cavity for the flow of cooling air.

In the alternative or additionally thereto, in the foregoing embodiment,the motor drive is disposed in the inner cavity, and the inner rotorsegment is disposed radially between the annular chamber and the innercavity.

In the alternative or additionally thereto, in the foregoing embodiment,the inner rotor segment defines a plurality of openings for the radialflow of cooling air from the inner cavity to the annular chamber.

In the alternative or additionally thereto, in the foregoing embodiment,the stator defines a plurality of openings for the radially outward flowof cooling air within the annular chamber.

In the alternative or additionally thereto, in the foregoing embodiment,the motor drive includes a circuit board as an integrated structuralcomponent of the stator.

The foregoing features and elements may be combined in variouscombinations without exclusivity, unless expressly indicated otherwise.These features and elements as well as the operation thereof will becomemore apparent in light of the following description and the accompanyingdrawings. However, it should be understood that the followingdescription and drawings are intended to be exemplary in nature andnon-limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

Various features will become apparent to those skilled in the art fromthe following detailed description of the disclosed non-limitingembodiments. The drawings that accompany the detailed description can bebriefly described as follows:

FIG. 1 is an disassembled, expanded, perspective view of anelectromagnetic machine as one non-limiting, exemplary embodiment of thepresent disclosure,

FIG. 2 is a perspective view of a stator of the electromagnetic machine;

FIG. 3 is a cross section of a bobbin of the stator;

FIG. 4 is a perspective view of a circuit board of the electromagneticmachine;

FIG. 5 is a schematic of a series coil configuration of the stator;

FIG. 6 is a schematic of a combination coil configuration of the stator;

FIG. 7 is a schematic of a parallel coil configuration of the stator;

FIG. 8 is a partial cross section of the electromagnetic machineillustrating a flow path of cooling air;

FIG. 9 is a schematic of another embodiment of a stator assemblyincluding a controller as part of a circuit board;

FIG. 10 is a cross section of another embodiment of the electromagneticmachine illustrated as an electric motor.

FIG. 11 is a side view of another embodiment of an electric coil of astator;

FIG. 12 is a top view of the electric coil in FIG. 11;

FIG. 13 is a schematic of a press used to bend the electric coil;

FIG. 14 is a perspective view of the stator utilizing the coils of FIG.11; and

FIG. 15 is a partial end view of a fan assembly utilizing the electricmotor.

DETAILED DESCRIPTION

Referring to FIG. 1, an electromagnetic machine 20 adapted to convertelectrical energy to mechanical energy, or vice-versa, is illustrated.Examples of the electromagnetic machine 20 may include an electric motorand a generator. The electromagnetic machine 20 may include a housing22, a motor drive 24, a stator 26, and a rotor 28. The housing 22 isadapted to house the circuit board 24, the stator 26, and the rotor 28.The circuit board 24 may be attached to the stator 26. As is generallyknown in the art of electric motors, the stator 26 and the rotor 28 areaxially aligned to one-another and are generally centered about arotation axis A. The stator 26 may be stationary, and the rotor 28 isadapted to rotate about the rotation axis A. Together, the circuit board24 and the stator 26 may be identified as a stator assembly 29. In oneexample, the electromagnetic machine 20 may be coreless. In another,non-limiting, example, the motor drive 24 may be, or may include, acircuit board that may be printed.

Universal Stator:

The stator 26 may include a support structure assembly 30, and aplurality of coils 32. The support structure assembly 30 may include amounting plate 34, bearings 36, a support structure 38, and a pluralityof bobbins 40 (see FIG. 2). Each one of the plurality of coils 32 may beone about a respective one of the plurality of bobbins 40. The supportstructure 38 is adapted to support, and attach to, the plurality ofbobbins 40. The mounting plate 34 may be adapted to support, and attachto, the support structure 38 and the bearings 36 for substantiallyfrictionless rotation of the rotor 28 about the axis A. The motor drive24 may attach to an axial side 42 of the mounting plate 34, and thesupport structure 38 may attach to an opposite axial side 44 of themounting plate. In another embodiment, the mounting plate 34 may be anintegral and unitary part of the support structure 38. In anotherembodiment, the mounting plate 34 may be an integral and unitary part ofthe motor drive 24 which may be a circuit board. In yet anotherembodiment, the stator 26 may not include the mounting plate 34, andinstead, the motor drive 24 as a circuit board also functions as astructural member from the stator 26.

Referring to FIGS. 2 and 3, the plurality of bobbins 40 may generally bethe same, with each including a core 50 extending along a centerline Cand two opposite flanges 52, 54. The core 50 extends between and mayform into the flanges 52, 54. The flanges 52, 54 may be substantiallynormal to the centerline C. When the electromagnetic machine 20 is fullyassembled, each centerline C may be generally normal to, and intersects,the axis A, and the coils 32 are generally wound about the respectivecores 50 and centerlines C. More specifically, each core 50 may extendin a radial direction with respect to axis A, such that the flange 52 isan outer flange, and the flange 54 is an inner flange located radiallyinward from the outer flange.

The support structure 38 may include at least one ring (i.e., twoillustrated as 46, 48). Both rings 46, 48 may be centered about axis A,and may be axially spaced apart from one another. Each bobbin 40 may beaxially elongated with respect to axis A, and may include opposite endportions 56, 58. When the support structure assembly 30 is assembled,the ring 46 may be an outer ring located radially outward from theplurality of bobbins 40, and the ring 48 may be an inner ring locatedradially inward from the bobbins 40. In one example and duringmanufacture, each coil 32 may be wound about a respective bobbin 40prior to attaching the bobbins 40 to the rings 46, 48. Moreover, eachbobbin 40 may be releasably attached to one, or both, of the rings 46,48 (e.g., snap fitted) for easy removal to perform maintenance on anyparticular bobbin 40 and/or coil 32.

Circuit Board with Multiple Coil Configuration Imprints:

Referring to FIG. 4, the motor drive 24 is generally illustrated as acircuit board that is substantially planar, circular and/or annular inshape, and substantially normal to axis A. The circuit board may be aprinted circuit board, and is generally configured to wire the pluralityof coils 32 in a predefined configuration to achieve, for example, thedesired output torque, and/or speed, of the electromagnetic machine 20.That is, the motor drive 24, as a circuit board, may enable the use ofuniversal components for multiple motor applications, by generallyproviding options on how the coils 32 are wired together (i.e., series,parallel, and combinations thereof). In one embodiment, the plurality ofbobbins 40 may each be the same, and may be universal bobbins capable ofbeing applied to a variety of motor applications with different outputparameters. Similarly, the stator support structure assembly 30, and/orthe support structure 38, may be universal, capable of being applied toa variety of motor applications utilizing the universal bobbins 40and/or universal coils 32.

Referring to FIGS. 4 through 7, the plurality of coils 32 (i.e., fourillustrated), may have a coil configuration 60 where the coils 32 areelectrically wired in series to one another (see FIG. 5), may have acoil configuration 62 where the coils 32 are electrically wired inparallel to one another (see FIG. 7), or may have a coil configuration64 where the coils 32 are electrically wired in a combination of bothparallel and series arrangements. The output of the motor torque andspeed may be different depending upon the coil configuration 60, 62, 64applied.

The motor drive 24 as a circuit board provides an easy and efficientmeans of choosing the desired coil configuration 60, 62, 64. Forexample, the circuit board may include a plurality of connection points66 (e.g., through-hole pads) and zero resistance jumpers, or printedtracers, 68 arranged to provide, for example, three individual coilconfiguration imprints (i.e., one illustrated in FIG. 4), with eachfootprint associated with a respective coil configuration 60, 62, 64.

As best shown in FIG. 2, the universal coils 32 may each includepositive and negative leads 70, 72, each projecting in a common axialdirection with respect to axis A. In general, lead 70 may be spacedradially outward from lead 72, and by a common radial distance for eachcoil 32. The leads 70, 72 may also be circumferentially spaced, by acommon circumferential distance, from the leads 70, 72 of thecircumferentially adjacent coil 32. In one embodiment, the leads 70, 72of the coils 32, may project axially through the mounting plate 32, andthrough the aligned connection points 66 for electrical connection tothe associated jumpers 68.

In one embodiment, the motor drive 24, as a circuit board, may generallyinclude three mountable positions 74, 76, 78, with each mountableposition associated with a respective coil configuration imprint. Duringmanufacture, or assembly, simply rotating the circuit board between themountable positions 74, 76, 78 is the means of selecting the desiredcoil configuration 60, 62, 64. More specifically, if the plurality ofcoils is twelve coils, the number of connection points 66 for leads 70may be three times the number of coils, which may be thirty-sixconnection points where only twelve are actually used. When used, theleads 70 may project axially through the respective through-hole pads 66for soldering to the respective tracer 68. The same principle may applyfor the leads 72. In another embodiment, the circuit board may includeonly one coil configuration imprint; however, to establish a desiredmotor type, the correct circuit board with the desired coilconfiguration imprint is chosen.

Inner Cooled Dual Rotor:

Referring to FIGS. 1 and 8, the rotor 28 may be a dual rotor having anouter rotor segment 75 spaced radially outward from, and concentric too,an inner rotor segment 77. Each segment 75, 77 may include a pluralityof permanent magnets 78 for interaction with the coils 32 as isgenerally known in the art of motors and generators. The outer and innerrotor segments 75, 77 may include boundaries that radially define anannular chamber 79. When the electromagnetic machine 20 is assembled,the outer rotor segment 75, the stator 26 is substantially in theannular chamber 79, the inner rotor segment 77 and the stator 26 (i.e.,bobbins 40 and coils 32) are generally axially aligned to one another,and the stator 26 is generally spaced radially from and between theouter and inner rotor segments 75, 77.

To provide air cooling for the stator 26, cooling air (see arrows 80 inFIG. 8) may flow through various channels, spaces, and/or gaps providedin and between the stator 26 and the rotor 28. In one embodiment, theinner rotor segment 77 and the stator 26 may include boundaries thatdefine a cooling flow gap 82 that may be substantially annular in shape,and is part of the annular chamber 79. The core 50 of each bobbin 40 mayinclude at least one cooling flow opening 84 (e.g., hole, sixillustrated in FIG. 3) that extend, or communicate, radially through thebobbin 40 with respect to axis A. The outer rotor segment 75 and thestator 26 may include boundaries that define a cooling flow gap 86 thatmay be substantially annular in shape, is part of the annular chamber79, and is located radially outward from gap 82. In addition, the outerrotor segment 75 may include boundaries that define a plurality ofopenings 88 (e.g., holes) that extend, or communicate, radially throughthe outer rotor segment 75 with respect to axis A.

When the electromagnetic machine 20 (e.g., motor) is assembled, the gap82 is in direct communication with the bobbin openings 84. The openings84 communicate directly with, and between, the gaps 82, 86, and the gap86 communicates directly with the outer rotor segment openings 88. Inoperation, cooling air 80 may flow axially through the gap 82, thenradially outward through the bobbin openings 84. From the bobbinopenings 84, the cooling air 80 may flow through the gap 86, thenradially through the outer rotor segment openings 88.

Self-Adapting Motor Drive:

Referring to FIGS. 1 and 9, another embodiment of the motor drive 24 ofthe stator assembly 29 may include a controller 90 configured to selectone of the coil configurations 60, 62, 64 based on sensory input. Thatis, the motor drive 24 may not include the multitude of configurationimprints previously described, and instead, may rely on the controller90 to select the appropriate coil configuration to optimize operation ofthe electromagnetic machine 20. In this embodiment, each coil lead 70,72 may still electrically connect to through-hole pads 66 as previouslydescribed in the example of the motor drive 24 being a circuit board;however, at least some of the zero-resistance jumpers, or tracers, maybe routed directly to a switch 92 of the motor drive 24.

The controller 90 may include a processor 94 (e.g., microprocessor) andan electronic storage medium 96 that may be computer readable andwriteable. A self-adapt logic module 98, which may be software-based, isstored in the electronic storage medium 96 and executed by the processor94 for control of the switch 92. Depending upon the selected, orcommanded, orientation of the switch 92, the plurality of electric coils32 may be orientated in one of the configurations 60, 62, 64.Non-limiting examples of the switch 92 may include a simple, mechanical,switch, at least one transistor switch, and/or a multitude ofmicro-switches. The motor drive 24 may further include other electronicelements 95 (see FIG. 10) as is known by those skilled in the art ofmotor drives.

Referring to FIG. 9, the sensor inputs may include one or more of atemperature signal 100 generated by a temperature sensor 102, a powersource input voltage signal 104 generated by a voltage sensor 106, atorque signal 108 generated by a torque sensor 110, a speed signal 112generated by a speed sensor 114, and other sensory inputs.

The controller 90 may further include a database 116 that includes aplurality of pre-programmed values (e.g., set points) utilized by theself-adapt logic module 98. In operation, the module 98 of thecontroller 90 may process the power source voltage signal 104 from thevoltage sensor 106, and based on the voltage, select an appropriate coilconfiguration to optimize performance based on a pre-programmed torqueand/or speed requirement stored in the database 116.

Alternatively, or in addition to, the module 98 of the controller 90 mayprocess the temperature signal 100 from the temperature sensor 102,which may be indicative of a stator temperature. The controller 90 maydetermine if, for example, the stator temperature is running high basedon a high temperature set point stored in the database 116. If thestator temperature is high, the controller 90 may choose a coilconfiguration appropriate to reduce the stator temperature, whilemaintaining torque and speed requirements as much as feasible.

Alternatively, or in addition to, the module 98 of the controller 90 mayprocess the torque signal 108 from the torque sensor 110. The torquesignal 108 may, for example, be indicative of an output torque of theelectromagnetic machine 20 (e.g., electric motor). This real-time outputtorque may be compared to a desired output torque pre-programmed intothe database 116. If the actual output torque is too high, or too low,the module 98 may cause the controller 90 to send a command signal (seearrow 118) to the switch 92 to appropriately re-configure the coils 32to achieve the desired torque. In one embodiment, the coil connectionsmay be switched, thus the coil configuration changed, while theelectromagnetic machine 20 (e.g., motor) is operating and the rotor 28is rotating about rotation axis A.

Alternatively, or in addition to, the module 98 of the controller 90 mayprocess the speed signal 112 from the speed sensor 114. The speed signal112 may, for example, be indicative of an output speed (e.g.,revolutions per minute) of the electromagnetic machine 20. Thisreal-time output speed may be compared to a desired output speedpre-programmed into the database 116. If the actual output speed is toohigh, or too low, the module 98 may cause the controller 90 to send acommand signal (see arrow 118) to the switch 92 to appropriatelyre-configure the coils 32 to achieve the desired speed.

Integrated Motor Drive:

Referring to FIGS. 1 and 10, another embodiment of an electromagneticmachine 20 is illustrated as an electric motor. The rotor 28 may be thedual rotor embodiment having the inner rotor segment 77 that carries acircumferentially continuous face 120 that faces radially inward andincludes boundaries that radially define an inner cavity 122. When theelectromagnetic machine 20 is fully assembled, the inner rotor segment77 is centered to axis A, the support structure 38 of the stator 26 isaxially aligned to, and spaced radially outward from the inner rotorsegment 77, and the outer rotor segment 75 is axially aligned to, andspaced radially outward from the stator support structure 38.

The support structure assembly 30 of the electromagnetic machine 20 mayfurther include a stationary shaft 124 that is centered to axis A,located in the inner cavity 122, generally axially aligned to the stator26 and rotor 28, and is spaced radially inward from the inner rotorsegment 77. The stationary shaft 124 may include opposite end portions126, 128 with the first end portion 126 engaged to the axial side 44 ofthe mount plate 34, and the opposite end portion 128 generally engagedto, or supporting, the bearings 36. The axial side 44 of the mount plate34 may include boundaries that, at least in-part, axially defines theinner cavity 122.

In one embodiment, the motor drive 24 may be located completely in theinner cavity 122 to optimize motor packaging. As illustrated in FIG. 10,the motor drive 24 may be the example of a circuit board that issupported by the stationary shaft 124 between the opposite end portions126, 128. In another embodiment, the motor drive 24 may be supported bythe mount plate 34 with any one or more of the controller 90, switch 92,and other electronic elements 95 projecting from the mount plate 34 andinto the inner cavity 122. For purposes of this embodiment, the term‘electronic elements’ may include the controller 90 and the switch 92.

In one embodiment, the stationary shaft 124 may be hollow having atleast one open end for the axial flow of the cooling air 80. In oneexample, the hollow shaft 124 may communicate through the mount plate 34of the support structure assembly 30. In another embodiment, the mountplate 34 may be closed off at the end proximate to the mount plate 34promoting further cooling air flow into the inner cavity 122.

In one embodiment, the mount plate 34 and/or the stationary shaft 124may be metallic to promote cooling of the motor drive 24 in the innercavity 122 via convection (i.e., heat sinks). In another embodiment, thehollow, stationary, shaft 124 may include boundaries that define atleast one opening 130 (e.g., hole) for the radially outward flow of thecooling air 80 from the hollow shaft 124, and into the inner cavity 122.Similarly, the inner rotor segment 77, the stator support structure 38,and the outer rotor segment 75 may each include a respective pluralityof openings 132, 84, 88 (e.g., holes, also see FIG. 8) for the radiallyoutward flow of cooling air 80. When the electromagnetic machine 20 isassembled, the inner cavity 122 is in fluid communication radiallybetween the openings 130, 132, the opening(s) 132 is in fluidcommunication radially between the inner cavity 122 and the opening(s)

When the electromagnetic machine 20 is fully assembled, a rotatingoutput shaft of the electromagnetic machine 20 may drive a motor fan asis known by one having skill in the art (not shown). The fan may drivethe air axially and radially outward through the inner cavity 122. Inthis way, the cooling air 80 may cool the motor drive 24 and the stator26.

Molded, Bobbin-less, Stator:

Referring to FIGS. 11 through 14, another embodiment of the stator 26 isillustrated along with a method of manufacture. The support structureassembly 30 of the present embodiment may not include the plurality ofbobbins 40 previously described, and the support structure 38 may notinclude the rings 46, 48. As best shown in FIG. 11, each electric coil32 may include an inner winding layer 134, a plurality of mid-windinglayers 136, and an outer winding layer 138, each electricallyinterconnected to form the coil 32. The inner winding layer 134 is woundabout, and radially spaced from, the centerline C, and includesboundaries that define the cooling opening 84. The mid-winding layers136 are located radially outward from the inner winding layer 134 withrespect to centerline C, with each successive mid-winding layer locatedradially outward from the adjacent mid-winding layer. The outer windinglayer 138 is located radially outward from the mid-winding layers 136,and generally represents an outer periphery of the coil 32.

Referring to FIGS. 11 and 12, generally, each of the winding layers 134,136, 138 may include diametrically opposite axial segments 140, 142, anddiametrically opposite circumferential segments 144, 146. The axialsegment 140 extends between, and is formed into, first ends of therespective circumferential segments 144, 146, and the axial segment 142extends between, and is formed into, opposite second ends of therespective circumferential segments 144, 146. When the stator 26 isassembled, the axial segments 140, 142 may each substantially extendaxially with respect to the rotation axis A, and the circumferentialsegments 144, 146 may be arcuate, each extending circumferentially withrespect to the rotation axis A.

The coil 32 may be further described having diametrically oppositeportions 148, 150 that may be substantially arcuate, and diametricallyopposite portion 152, 154 that may be substantially linear, or straight.Arcuate portion 148 may extend between, and generally forms into ends ofthe respective straight portions 152, 154, and the arcuate portion 150may extend between, and generally forms into opposite ends of therespective straight portion 152, 154. Each portion 148, 150, 152, 154may include a respective plurality of the segments 144, 146, 140, 142.In another example, the coil 32 may be substantially circular or oval,thus the portions 152, 154 may not be straight. Examples of a windingmaterial, or shape, may be electrically conductive, profiled, wire, andtapes or ribbons that increase fill factors.

During manufacturing, each coil 32 may be wound about the centerline C,separately, and generally within a plane. That is, the portions 148, 150may initially be straight or flat, and without an arcuate shape. Thewound coil 32 may then be bent to provide the arcuate shape of theportions 148, 150. Referring to FIG. 13, and in one example, the un-bentcoil 32 may be placed into a press, or similar tool, 156 to obtain thearcuate shape.

Referring to FIGS. 11 and 14, with the coils 32 fully formed, or shaped,each coil 32 may be circumferentially placed about the rotation axis A.When properly positioned, the axial segment 142 of a first coil 32 islocated proximate to the axial segment 140 of a circumferentiallyadjacent second coil 32. The coils 32 may then be secured to one-anotherutilizing a bonding material 158 while preserving the cooling openings84.

In one embodiment, the bonding material 158 may be applied while thecoils 32 are properly orientated within a mold (not shown). Such a moldmay support an injection molding process. Examples of the bondingmaterial 158 may be an adhesive, thermoplastic, injection moldingplastic, or other materials having electrically insulating properties.

Advantages and benefits generally specific to the molded stator mayinclude the allowance of a reduced radial thickness of the stator,smaller air gaps, an increase in space that can be used for the coil,enabling the use of less expensive magnets as ferrites, enables directcooling of coils, and a reduction in material costs with respect to thestator.

Dual Rotor, Coreless, Electromagnetic Machine Architecture:

The electromagnetic machine 20 may be coreless, and may include the dualrotor 28. The novel architecture of the electromagnetic machine 20, aspreviously described, provides a structural solution for a wide range ofapplications including, but not limited to, a fan driving motor familycovering different voltage inputs, shaft power, torque, and RPM. Thearchitecture may be designed as an external rotor solution or a shaftdriven solution.

The architecture may generally be of a modular design that simplifiesmanufacturing and maintenance. The electromagnetic machine architecturemay utilize sintered magnets, or molded rotor structures. Thearchitecture may further include back iron, or may benefit from apermanent magnet Halbach array arrangement, and use such as a structuralcomponent of the electromagnetic machine 20.

Referring to FIG. 15, an example of an external rotor solution isillustrated as a fan assembly 160 that includes the electromagneticmachine 20 as an electric motor, and a plurality of air foils, orblades, 162 projecting radially outward from the outer rotor segment 75of the dual rotor 28.

Advantage and benefits regarding the electromagnetic machinearchitecture include scalability to achieve desired torque and/or speed,a lack of cogging torque, a lack of core losses, less load on bearings,extended life, and the modular design. Another advantage is a negligiblemagnetic pull forces thus a simplified support structure, lowsensitivity to rotor imbalance, and/or rotor-to-stator misalignment.

Other general advantages and benefits of the present disclosure includea reduction in design and manufacturing costs, a single coil windingtype for an entire family of motors, coil connections conducted on acircuit board, utilization of a circuit board as part of a structuralmember, optimized motor packaging, and improved stator and motor drivecooling. Other advantages include the ability to wind the coilsindividually, or separately, on a rotary winding machine duringmanufacture to achieve higher fill factors, and the use of bobbinmounting rings or clips for quick assembly of the stator. Yet anotheradvantage is the ability to change coil configurations dynamically tomeet, for example, the currently required speed of a fan to optimize themotor performance.

While the present disclosure is described with reference to the figures,it will be understood by those skilled in the art that various changesmay be made and equivalents may be substituted without departing fromthe spirit and scope of the present disclosure. In addition, variousmodifications may be applied to adapt the teachings of the presentdisclosure to particular situations, applications, and/or materials,without departing from the essential scope thereof. The presentdisclosure is thus not limited to the particular examples disclosedherein, but includes all embodiments falling within the scope of theappended claims.

What is claimed is:
 1. A coreless electromagnetic machine comprising: adual rotor adapted to rotate about an axis, the dual rotor includinginner and outer rotor segments, wherein the outer rotor segment isspaced radially outward from and axially aligned to the inner rotorsegment, and the inner and outer rotor segments radially define anannular chamber; and a stator disposed at least in-part in the annularchamber, wherein the coreless electromagnetic machine is a corelesselectric motor, wherein each one of the first and second rotor segmentsinclude a plurality of permanent magnets, and wherein the statorincludes a plurality of electric coils each including an inner windinglayer wound about and spaced from a centerline that generally intersectsthe axis, and the inner winding layer defining an opening for the flowof cooling air between the annular inner and outer gaps.
 2. The corelesselectromagnetic machine set forth in claim 1, wherein the plurality ofpermanent magnets are sintered magnets.
 3. The coreless electromagneticmachine set forth in claim 1, wherein the plurality of permanent magnetsare molded magnets.
 4. The coreless electromagnetic machine set forth inclaim 1, wherein the outer rotor segment and the stator radially definean annular outer gap as part of the annular chamber, and the inner rotorsegment and the stator radially define an annular inner gap as part ofthe annular chamber.
 5. The coreless electromagnetic machine set forthin claim 1, wherein each one of the plurality of electric coils includea plurality of mid-winding layers disposed radially from the innerwinding layer, and an outer winding layer disposed radially outward fromthe plurality of mid-winding layers with respect to the centerline. 6.The coreless electromagnetic machine set forth in claim 1, wherein thestator includes a bonding material for securing the plurality ofelectric coils together.
 7. The coreless electromagnetic machine setforth in claim 6, wherein the bonding material is molded to theplurality of electric coils.
 8. The coreless electromagnetic machine setforth in claim 4, wherein the stator includes a support structure, aplurality of bobbins detachably fitted to the support structure, and aplurality of electric coils with each one wound about a respectivebobbin of the plurality of bobbins.
 9. The coreless electromagneticmachine set forth in claim 8, wherein each bobbin of the plurality ofbobbins define an opening for the flow of cooling air radially betweenthe annular inner and outer gaps.
 10. A coreless electromagnetic machinecomprising: a dual rotor adapted to rotate about an axis, the dual rotorincluding inner and outer rotor segments, wherein the outer rotorsegment is spaced radially outward from and axially aligned to the innerrotor segment, and the inner and outer rotor segments radially define anannular chamber; a stator disposed at least in-part in the annularchamber, wherein the coreless electromagnetic machine is a corelesselectric motor, wherein the stator includes a plurality of electriccoils each including an inner winding layer wound about and spaced froma centerline that generally intersects the axis, and the inner windinglayer defining an opening for the flow of cooling air between theannular inner and outer gaps; and a motor drive disposed in an innercavity axially aligned to and defined by the inner rotor segment,wherein the inner rotor segment is radially disposed between the innercavity and the annular chamber.
 11. The coreless electromagnetic machineset forth in claim 10, wherein the motor drive includes a circuit boardelectrically connected to each one of the plurality of electric coils.12. A coreless electric motor comprising: a dual rotor adapted to rotateabout an axis, the dual rotor including inner and outer rotor segmentseach including a plurality of permanent magnets, wherein the outer rotorsegment is spaced radially outward from and axially aligned to the innerrotor segment, and the inner and outer rotor segments radially define anannular chamber; a stator disposed at least in-part in the annularchamber, and including a plurality of electric coils, wherein theplurality of electric coils each include an inner winding layer woundabout and spaced from a centerline that generally intersects the axis,and the inner winding layer defining an opening for the flow of coolingair between the annular inner and outer gaps; and a motor driveelectrically connected to each one of the plurality of electric coils.13. The coreless electric motor set forth in claim 12, wherein the innerrotor segment radially defines an inner cavity for the flow of coolingair.
 14. The coreless electric motor set forth in claim 13, wherein themotor drive is disposed in the inner cavity, and the inner rotor segmentis disposed radially between the annular chamber and the inner cavity.15. The coreless electric motor set forth in claim 14, wherein the innerrotor segment defines a plurality of openings for the radial flow ofcooling air from the inner cavity to the annular chamber.
 16. Thecoreless electric motor set forth in claim 12, wherein the motor driveincludes a circuit board as an integrated structural component of thestator.